[mc-devel] [PATCH] Prefer $() to backticks in sh script

[Yury V. Zaytsev]

> On 2. Nov 2024, at 11:06, Matěj Cepl via mc-devel <mc-devel at lists.midnight-commander.org> wrote:
> 
> Both of them are perfectly standard [1], but my old eyes really
> prefer the command substitution syntax.

They are both POSIX, but not all systems support POSIX in the same way. Notably, the default /bin/sh on Solaris is not XPG4-compliant. I don’t think making it easier on your old eyes is a good argument for knowingly introducing portability problems. I’d rather switch all scripts that are supposed to run under /bin/sh and not bash to backticks. Unfortunately, nobody was really paying attention so far, and scripts were only being edited as they broke:

diff --git a/src/vfs/extfs/helpers/iso9660.in b/src/vfs/extfs/helpers/iso9660.in
index e5d41dafe..784a62415 100644
--- a/src/vfs/extfs/helpers/iso9660.in
+++ b/src/vfs/extfs/helpers/iso9660.in
@@ -32,7 +32,7 @@

#*** file scope functions **********************************************

-XORRISO=$(command -v xorriso 2>/dev/null)
+XORRISO=`command -v xorriso 2>/dev/null`

# This snippet is used to undo xorriso's Text_shellsafe(). Pseudocode for the
# function:
@@ -49,7 +49,7 @@ XORRISO=$(command -v xorriso 2>/dev/null)
# - iso_tree.c:Xorriso_ls()
# - text_io.c:Xorriso_esc_filepath()
# - misc_funct.c:Text_shellsafe()
-awk_xorriso_unesc=$(cat <<'EOF'
+awk_xorriso_unesc=`cat <<'EOF'
{
# Start of the path part
i = index($0, "'")
@@ -78,14 +78,14 @@ awk_xorriso_unesc=$(cat <<'EOF'
print substr($0, 1, i-1) s
}
EOF
-)
+`

xorriso_list() (
if test -z "$XORRISO"; then
return 1
fi

- temp_ls=$(mktemp "${MC_TMPDIR:-/tmp}"/mc-iso9660.XXXXXX) || return 1
+ temp_ls=`mktemp "${MC_TMPDIR:-/tmp}"/mc-iso9660.XXXXXX` || return 1

# $XORRISO must be unquoted here to hook into the testing framework
$XORRISO -abort_on FATAL -dev stdio:"$1" -find / -exec lsdl 2>/dev/null >"$temp_ls"
@@ -143,18 +143,18 @@ xorriso_rm() {

# tested to comply with isoinfo 2.0's output
test_iso () {
- ISOINFO=$(command -v isoinfo 2>/dev/null)
+ ISOINFO=`command -v isoinfo 2>/dev/null`
if test -z "$ISOINFO"; then
echo "isoinfo not found" >&2
return 1
fi

- CHARSET=$(locale charmap 2>/dev/null)
+ CHARSET=`locale charmap 2>/dev/null`
if test -z "$CHARSET"; then
- CHARSET=$(locale 2>/dev/null | grep LC_CTYPE | sed -n -e 's/.*\.\(.*\)"$/\1/p')
+ CHARSET=`locale 2>/dev/null | grep LC_CTYPE | sed -n -e 's/.*\.\(.*\)"$/\1/p'`
fi
if test -n "$CHARSET"; then
- CHARSET=$(echo "$CHARSET" | tr '[A-Z]' '[a-z]' | sed -e 's/^iso-/iso/')
+ CHARSET=`echo "$CHARSET" | tr '[A-Z]' '[a-z]' | sed -e 's/^iso-/iso/'`
$ISOINFO -j $CHARSET -i /dev/null 2>&1 | grep "Iconv not yet supported\|Unknown charset" >/dev/null && CHARSET=
fi
if test -n "$CHARSET"; then
@@ -163,13 +163,13 @@ test_iso () {
JOLIET_OPT="-J"
fi

- ISOINFO_D_I="$($ISOINFO -d -i "$1" 2>/dev/null)"
+ ISOINFO_D_I=`$ISOINFO -d -i "$1" 2>/dev/null`
ISOINFO="$ISOINFO -R"

echo "$ISOINFO_D_I" | grep "UCS level 1\|NO Joliet" > /dev/null || ISOINFO="$ISOINFO $JOLIET_OPT"

- if [ $(echo "$ISOINFO_D_I" | grep "Joliet with UCS level 3 found" | wc -l) = 1 \
- -a $(echo "$ISOINFO_D_I" | grep "NO Rock Ridge" | wc -l) = 1 ] ; then
+ if [ `echo "$ISOINFO_D_I" | grep "Joliet with UCS level 3 found" | wc -l` = 1 \
+ -a `echo "$ISOINFO_D_I" | grep "NO Rock Ridge" | wc -l` = 1 ] ; then
SEMICOLON="YES"
fi
}
@@ -190,7 +190,7 @@ mcisofs_list () (
*) MYCAT="cat";;
esac

- lsl=$($ISOINFO -l -i "$1" 2>/dev/null)
+ lsl=`$ISOINFO -l -i "$1" 2>/dev/null`
r=$?
test $r -gt 0 && return $r

diff --git a/src/vfs/extfs/helpers/uarj.in b/src/vfs/extfs/helpers/uarj.in
index 15549a026..99c5c9e57 100644
--- a/src/vfs/extfs/helpers/uarj.in
+++ b/src/vfs/extfs/helpers/uarj.in
@@ -16,7 +16,7 @@ ARJ="arj -+ -ja1"

mcarjfs_list ()
{
- $ARJ v "$1" | @AWK@ -v uuid=$(id -ru) '
+ $ARJ v "$1" | @AWK@ -v uuid=`id -ru` '
{ 
if (($0 ~ /^[0-9]+\) .*/)||($0 ~ /^------------ ---------- ---------- -----/)){
if (filestr ~ /^[0-9]+\) .*/) {
diff --git a/src/vfs/extfs/helpers/uha.in b/src/vfs/extfs/helpers/uha.in
index 9dd0016bc..405f72d49 100644
--- a/src/vfs/extfs/helpers/uha.in
+++ b/src/vfs/extfs/helpers/uha.in
@@ -10,7 +10,7 @@ HA=ha

mchafs_list ()
{
- $HA lf "$1" 2>/dev/null | @AWK@ -v uid=$(id -ru) '
+ $HA lf "$1" 2>/dev/null | @AWK@ -v uid=`id -ru` '
/^===========/ {next}
{
if ($5="%" && $8~/DIR|ASC|HSC|CPY/) {
diff --git a/src/vfs/extfs/helpers/uzoo.in b/src/vfs/extfs/helpers/uzoo.in
index fb079a5ad..5f00e7973 100644
--- a/src/vfs/extfs/helpers/uzoo.in
+++ b/src/vfs/extfs/helpers/uzoo.in
@@ -23,7 +23,7 @@ mklink ()
mczoofs_list ()
{
mklink "$1"
- $ZOO lq "$ARCHIVE" | @AWK@ -v uid=$(id -ru) '
+ $ZOO lq "$ARCHIVE" | @AWK@ -v uid=`id -ru` '
/^[^\ ]/ { next }
{
if (NF < 8)